Small scale hybrid engine (SSHE) utilizing fossil fuels

ABSTRACT

This invention describes a miniaturized hybrid diesel-electric engine formed by a closed-loop system powered by plasma-aided combustion of JP-8 fuel (or other hydrocarbon fuels) working in tandem with a vapor cycle utilizing miniaturized expanders and condensers. The output of this engine is electric power and mechanical work. Water, or organic fluids, heated by the combustion product developed inside a special burner, undergoes an explosive, quasi-supersonic conversion to steam. This steam drives a high-speed turbine connected together with a gas turbine outputting shaft work. This work output is utilized to power internal subsystems, cool down the miniaturized condensers, and to produce torque and electric power. The dimensions of this miniaturized hybrid-engine are so compact that it can fit inside the battery compartment of most applications requiring high-density miniaturized power sources.

BACKGROUND OF THE INVENTION

The conversion of compact gasoline spark ignition engines to diesel orheavy-fuels operated engines for various applications requiringminiaturized power sources, including robotics and exoskeleton, andsmall scale propulsion system, forces a series of adaptation of thecurrent off-the-shelf engines. These adaptations allow a conventionalminiaturized gasoline engine to be fueled by heavy-fuels at the expenseof significant inefficiencies. Most of these diesel operated gasolineengines have serious ignition difficulties, especially at sub-zerotemperatures, and generally show poor performance with respect to theactual power available for energy extraction from the fuel. Furthermore,increased fuel consumption with production of heavy smoke and pollutantemissions, and several other negative factors, severely penalizes theadoption of these modified engines. The need for air-breathingsmall-scale propulsion systems, with high power densities for civilianand military applications is ever increasing. The objective of thepresent invention is to provide a small-scale hybrid-engine (SSHE)formed by the integration of several technologies allowing itsminiaturization without impairing the overall engine efficiency.

A secondary objective of the proposed invention is that of providing awearable power source equipped with its own fuel tank, pumps, startermechanisms, mufflers, injectors, etc. This wearable, or mobile, SSHEsystem can deliver a minimum of 20 W average for prolonged amounts oftime with minimum fuel consumption, and load following characteristics.SSHE can also produce a scalable power output able to achieve and exceedthis minimum power requirement so that it can serve multipleapplications. Such applications may require a power source for powerhungry systems such as microclimate cooling with power requirements inexcess of 1200 W-hr, or able to provide shaft power for actuators usedfor robotic applications, or as a propulsion system for remotelycontrolled vehicles. Load following characteristics imply a rigorouscontrol of the various combustion parameters forcing a fast response onthe rotating components of the burner. All components are designed forminimum weight and bulk. Components like miniaturized compressor andexhaust gases wheels impose high degrees of manufactory accuracy andcomplexity. All of the components of this invention can function in awide range of temperatures and environments, including submerged inwater, while resisting to shocks derived from mechanical impacts orexplosions. The complete system is reliable and damage-tolerant, posingno hazards to the operator.

To meet these requirements, technology has been pushed beyond itscurrent limits and the integration of several innovative conceptsproduced the SSHE. Every ounce of mass of the SSHE system contributes toperformance, and every watt of thermal, electrical, or mechanical powergenerated is applied with the highest conversion efficiency. These arethe main objectives of the SSHE proposed as a miniaturized power sourceutilizing fossil fuels.

SUMMARY OF THE INVENTION

The heart of the Small Scale Hybrid Engine (SSHE) is a specialfluid-expanding cavity thermally coupled with a plasma-aided hydrocarbonburner equipped with a U-turn combustion gases circuit. The combustioncycle executed by the burner works in tandem with a Rankine-like vaporcycle operating between a hot source formed by the combustion productsand a cold source formed by a heat transfer mechanism between the burnerintake air and special condensation cavities. The cold source is ahighly conductive-to-convective heat transfer surface in thermal contacton one side with the large mass flow rate of intake air. This condensingcavity discharges the excess heat from the working fluid in a closedloop to the environment while providing the muffler structure of theburner capsule for sound abatement. Efficiency of the vapor-combustioncycle is estimated at approximately 54% for a JP-8 fueled SSHE.Combustion energy is also stored in the mass of the thermal reservoirstructure forming a thermal flywheel, and can rapidly be converted intopressure and mechanical work, using the fluid expanding cavity whichachieves extremely high heat transfer rates from the thermal reservoirto said working fluid. The heat energy thus transferred to said workingfluid is applied to an electronically controlled alternator/starterwhose rotor is embedded in the vapor turbine or in a separate disk forelectric production. Said vapor turbine is also mechanically linked toan exhaust gas turbine driven by the expansion of combustion gasesinside the core of the burner structure. Said turbines produce torquefor electric production as well as shaft power mechanically transferredvia geared coupling for different rpm between the turbines themselveswhile providing a mechanical coupling for a torque output of the SSHE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 s a schematic representation of the SSHE internal structures withflow lines indicating the combustion gases circuit and the vapor-cycleformed by a closed loop integrating the working fluid tank, sealedhydraulic connections, pump(s), double counter flow fluid expanding heattransfer system, and the condensing cavities.

FIG. 2 is a schematic representation of the SSHE internal structureswith flow lines indicating mainly the fossil fuel burning cycle formedby special fuel expanding injection, ionization, and ignition systems, aU-turn exhaust gas circuit coupled with high heat transfer rate workingfluid expanding systems. Said fossil fuel burning cycle including fueltank, pump, starter all self contained inside the SSHE structure.

FIG. 3 is a schematic representation of the electric alternator/starterembedded inside the SSHE rotating components, showing the position ofrare earth magnets, coils, and the electronic controller.

FIG. 4 is a block diagram of the CPU control system all integrated in aprinted circuit.

FIG. 5 is a representation of a complete SSHE unit showing the turbineassembly and the cylindrical nature of all cavities within which theworking fluid expands and condenses while the exhaust gases transferheat inside the burner.

FIG. 6 is a representation of a complete SSHE unit assembled inside apower pack having dimensions similar to those offered by a typicalbattery for the high density power output.

FIG. 7 is a representation of a complete SSHE unit integrated inside acompact self sustained power pack showing a mechanical coupling able totransfer shaft power to external mechanical applications (i.e.compressors, impeller, propellers, pulleys, etc.) while still able toprovide electric power at its output.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The working principles of the SSHE system are now described by utilizingthe schematics and representations shown in FIGS. 1–7.

In FIG. 1, two cylindrical fluid expanding cavities 1 and 1 a, shown incross-section view, are assembled around the basic structure of the SSHEcombustion chamber 4. The body of the fluid-expanding cavity 1 a isformed by concentric and sealed cylinder-like structures separated by agap within which the working fluid 10 contained inside a toroidalstorage tank 11 expands. Tank 11 shown in FIG. 1 is not to scale.Similarly, the body of fluid-expanding cavity 1 is formed by concentricsealed cylinders internally separated by a gap within which the workingfluid 10 expands. Said working fluid 10 is pumped at relativelyhigh-pressure inside the fluid expanding cavity 1 a through one or morehigh-pressure miniaturized pump(s) 8 geared through a gear assembly 12to a set of turbines 13, 14, and 15 linked to the same shaft 9. Thehigh-pressure pump 8 is a piston driven positive displacement pump. Eachstroke of pump 8 delivers an amount of working fluid 10 proportional tothe rotating speed of shaft 9. Pump 8 is hydraulically connected to ahigh-pressure fluid injector 16 acting as a check valve. When pump 8 isset in motion by the alternator/starter system 23 (shown in FIG. 3),high pressure working fluid 10 is throttled inside the fluid-expandingcavity 1 a through check valve 16. Sub-cooled liquid working fluid 10 isnow exposed to a heat transfer thermodynamic process since the innersurfaces of said fluid-expanding cavity 1 a are in thermal contact withthe combustion gases 19 produced inside combustion chamber 4. The outersurfaces of fluid-expanding cavity 1 a are kept at almost adiabaticconditions by means of thermally insulating materials 17 surroundingfluid-expanding cavity 1 a and 1. The working fluid 10 exits fluidinjector 16 and expands in a counter-flow fashion with respect to thedirection of the hot combustion gases 19. It reaches the bottom of theburner structure 20 and enters hydraulic connections 2 disposed radiallyand exposed to the high temperatures of the combustion gases 19, withoutmixing with said gases. These hydraulic connections 2 allow theexpanding fluid 10 from cavity 1 a to enter fluid-expanding cavity 1 andundergo an additional heat transfer and thermodynamic process toincrease its energy content. While transiting inside fluid-expandingcavity 1 in a counter-flow fashion with respect to the direction of thecombustion gases 19, heat transfer occurs through the inner walls andsurfaces of fluid-expanding cavity 1 so that at its outlet 5 the workingfluid 10 is at high pressures and temperatures, in a superheated state.Fluid expanding cavity 1 is thermally insulated from the air intakemanifold cavity 18 surrounding the structure of said fluid expandingcavity 1. Through hydraulic and sealed connection between 5 and 5 a (seealso FIG. 3), said superheated working fluid is allowed to expandthrough one or more nozzles 6 into a set of high-pressurevapor-turbine(s) 14 co-axially and mechanically linked with shaft 9. Themechanical connection of said vapor turbine 14 can be directly coupledto shaft 9, or indirectly coupled to shaft 9 by means of gear changingthe speed ratio. At the outlet of blades 7 of turbine(s) 14 the expandedworking fluid 10 flows through hydraulic vapor venting connections 21inside a condensing cavity 22 surrounding all other cavity structures.The condensing cavity 22 is formed by concentric cylinder-like sealedand positioned so as to form a gap in between the outer surface of theinner cylinder and the inner surface of the outer cylinder. Inside thisgap the expanded working fluid 10 releases heat to the intake airmanifold via the inner walls of said condensing cavity 22 without mixingwith said intake air. The expanded working fluid 10 also releases heatto the outer wall of said condensing cavity 22 via natural or forcedconvection with the environment surrounding said condensing cavity 22through fins 22 a positioned radially along the SSHE body. The expandedfluid 10 releases heat along the whole length and surfaces of thecondensing cavity 22 such that the induced temperature drop causes theexpanded working fluid 10 to return to a sub-cooled liquid state. Thesuction of pump 8 can be positioned anywhere along the working fluidcollective tank formed by tank 11, surrounding the top structure of theSSHE, the hydraulic connections to the condensing cavity 22, and insidethe gap itself of condensing cavity 22. Shaft 9 is also geared to a setof speed reducing/increasing gears 45 (more in detail in FIG. 3), whichprovide speed adjustment for the different turbines 13, 14, and 15 and amechanical outlet equipped with a coupler 44 so as to provide externalshaft power to the user at the desired torque and rpm. This concludesthe closed loop SSHE vapor cycle of working fluid 10 described in FIG. 1and FIG. 3.

The burner side of the SSHE system is best described in FIG. 2. At thetop of FIG. 2, the electric alternator/starter formed by a rotating disk23 receives shaft power from shaft 9 whose torque magnitude is theresult of the expansion of combustion gases 19, produced in thecombustion chamber 4, and the expansion of working fluid 10 through thehigh-pressure vapor turbine(s) 14. Air 24 enters the SSHE from an airfilter 25 positioned above the intake of compressor turbine 13. Toreduce acoustic signature caused by the inlet air-flow, and especiallyby the high speed (10,000 rpm range) of the compressor turbine 13, theinner walls of the intake manifold are lined with sound absorbingmaterials 26′, thereby forming the intake muffler 27′. For a 20W-electric power output the overall weight of the SSHE rotating parts islow enough to make gyroscopic effects negligible. The air filter 25 canbe positioned on the circumference of the SSHE or anywhere along theintake air path. In both cases the SSHE inlets can be made water sealedby turning said air filter casing 27″ or by pressing it against thecompressor wheel 13 inlet. When this operation is executed, an air-flowsensor embedded anywhere in the air intake path utilized by the SSHEcomputer controller 25 a for fuel metering purposes detects the rapidchange in inlet pressure, and the SSHE fuel control system immediatelydeactivates the fuel pump 8 a or the fuel vaporizing and injectingsystem 27 and 27 a to shut down the burner. This feature allows thesubmersion of the SSHE, while electric power is still provided bystart-up and back-up batteries 28. The capacity of these batteriesdetermines the time the SSHE can be submerged and still provide fullpower to the user. For a 20-Watt average power demand a relatively smallion-lithium battery 28 used to start the SSHE can maintain the requiredpower output for several hours with the SSHE burner in shut-down mode.The bearings (not shown in FIG. 2) for the compressor turbine 13 and thealternator/starter shaft (coupled directly or indirectly with driveshaft 9), can be made of self-lubricating materials, or lubricated by aclosed loop oil circulation system geared with the drive shaft 9.

When air 24 enters the suction side of the compressor turbine 13, itundergoes a compression process while channeled into the jacket-likehydraulic structure 18 surrounding the burner. Structure 18 forms acavity in thermal contact with the condensing cavity 22 but thermallyinsulated from combustion gases 19. In this manner, a relatively largemass flow of cold air is forced into contact with the surfaces of thecondensing cavity 22 which, in this configuration, is also utilized as adevice to cool down the exhaust gases to reduce thermal signature bybleeding cold air through calibrated orifices 33 a. Through thecompressor turbine 13, compressed air 24 is available at the inlet 29 ofthe burner 4 where mixing with a superheated JP-8 vapor jet occurs. Thisjet of fuel vapors is produced by a miniaturized heat expanding fuelinjection system 27 which converts liquid fuel into superheated fuelvapor instantaneously. Fuel 30 is stored in a semi-toroidal tank 30 a(not to scale), positioned above and surrounding the structure ofcompressor turbine 13, and pumped into heat expanding fuel system 27through fuel pump 8 a. At start-up the heat expanding fuel injectionsystem 27 is electrically heated through a heater 27 a powered viaelectronic control from CPU circuit 25 a by the start-up battery 28.Soon after ignition of the burner the temperature of this heat expandingfuel injection system 27 is kept at the proper level through heattransferring from the exhausting combustion gases 19. At the burnerinlet 29, JP-8 vapors and air undergo a violent ionization showerthrough symmetrical electrodes 31 powered by a controlled cold plasmagenerator 32′. Ionized species formed via cold corona discharge increasemixing favoring combustion while containing the air fuel mixture awayfrom the metal walls of the surrounding structure to minimize fuelcondensation. An instantaneous wall of approximately 5,000° C.plasma-flame is then formed in front of the ionized mixture through hotplasma electrodes 32 controlled by a hot plasma generator and controller33. The ionized air fuel mixtures ignites and expands in the combustionchamber 4. Virtually any fuel available will ignite under theseconditions, thereby SSHE can operate with several types of liquid orgaseous fuels. While expanding, the high-pressure, high-temperatureexhaust combustion gases 19 enter the exhaust gas turbine 15 poweringthe alternator/starter system 23 and the compressor wheel 13 in tandemwith the torque generated by the vapor cycle through high-pressureturbine(s) 14. The shaft work generated by the combustion process alsoprovides power to the fuel-pump 8 a geared with the exhaust gas turbine15 via drive shaft 9. Exhaust combustion gases 19 circulate inside thebody of the SSHE and transfer heat to the surfaces of the condensingcavity 1 a and 1. To decrease thermal signature due to the hightemperature of the exhaust gases 19 these gases can be mixed with coldair 24 bled from the compressed air burner intake manifold 33 a. Thisprocess is inefficient, but provides significant cooling to the exhaustgases 19 before they enter the muffler 34. Said muffler 34 is lined withsound absorbing materials 26, thereby reducing thermal and acousticsignature. Therefore, exhaust combustion gases 19 will exit the SSHEunit with reduced temperature and noise since the outlet muffler 34 islined with sound absorbing materials 26 shaped to reduce the soundproduced by the combustion processes and the turbines operation. Aflexible membrane 35′ is positioned at the outlet of the muffler 34forming a check valve automatically sealing the SSHE when submerged.Overall, the SSHE is designed with multiple barriers to heat and sound.The fluid expanding cavities 1 a and 1, and the condensing cavity 22 bybeing formed by series of concentric cylinders become a heat and soundshield while making the SSHE structure extremely compact and damagetolerant.

In FIG. 3, the SSHE electric power generator or alternator and starteris shown. This electric alternator is an electronically controlledalternator-starter formed by a rotating disk 23 symmetrically containingmagnets 35, magnetically coupled with symmetrical stationary coils 36.As shown in FIG. 3, representing the “head” of the SSHE, a series ofmultiple permanent magnets such as Ferroxdure, consisting of anisotropicsintered barium, or similar materials, are positioned on thecircumference of the rotor or embedded with disk 23. Similar results canbe obtained by embedding said permanent magnets 35 with the aircompressor wheel 13, or vapor turbine 14, or exhaust gas turbine 15 inwhich case the rotor disk 23 is not necessary. The symmetric coils 36 ofthis alternator are embedded in the SSHE head housing or stator. Thesecoils are connected to a bridge of high-frequency switching transistors(i.e., power MOSFET) driven by a custom made specialized computer 37controlled by CPU system 25. The printed circuit containing all of theelectronic components for the CPU system 25 (CPU card) is positioned inthe vicinity of the rotor disk 23. The electric connections from thecoils 36 to the power MOSFET 38 are extremely short to minimizeelectromagnetic noise production as a result of the fast switching.MOSFET 38 are exposed on one side to the intake air-flow throughsymmetrical fins 38 a, thereby providing cooling. The electronic circuitutilizes electromagnetic interference suppression technologies (i.e.,surface mount ferrite bead EMI) and an internal switching power supplyto minimize irradiation of electromagnetic noise to the electronicsystems feeding from the SSHE. The heat generated by the coils andMOSFET 38 switching is easily removed by fins 38 a exposed to the highrate flowing of air 24 at the discharge of the compressor turbine 13. Athermal barrier 46 insulates the electronic equipment of the alternatorassembly formed by the rotating disk 23, printed circuit 37 includingCPU system 25 formed by microchips, components, sensors, etc. Thermalbarrier 46 also insulates the air intake circuit to avoid unwantedheating of the air through heating of the metal rotating components suchas the exhaust combustion gas turbine 15. For these reasons drive shaft9 is formed by at least two parts or shafts coupled and concentric.Drive shaft 9 is made to withstand high temperatures, while concentricshaft 9 a, essentially prolonging shaft 9, is designed to thermallyde-couple the high-temperature side of the SSHE from the low temperatureside.

In FIG. 4, the electronic system diagram block is shown. The electroniccontrol system is primarily composed of sensors and actuators designedto provide the CPU with the required information to regulate the outputof the SSHE. The entire CPU structure indicated by the block diagram inFIG. 4 can be assembled with high degree of miniaturization and fit inthe printed circuit board 25 located in the vicinity of the rotatingalternator disk 23.

At the heart of the system, the CPU is responsible for the properoperation of the entire unit. The SSHE unit can be operated in differentmodes: start-up, shut-down due to submersion, shut-down due to silentmode operation, or in automatic mode which shuts-down the unit if theintake air flow sensor detects an irregular change in the air pressure.The CPU gathers the user input (startup, shutdown, silent mode,automatic mode), along with the current electrical or mechanical loadingneeds of the system, and adjusts the actuators to provide the desiredeffect. The CPU is constantly communicating with the Power System whosejob is to regulate the available power based on the CPU's commands. ThePower System receives power from both the battery 28 and thealternator/generator formed by the assemblies including disk 23, andwill combine the two to provide the required output power. The system isdesigned such that only one power source (alternator/starter 23 orbattery 28) is actually needed to provide the rated power, and thus, anyexcess power can be used to either start the SSHE burner or chargebattery 28 for use in silent or automatic modes.

When the power output required by the SSHE is increased, the battery 28(FIG. 2), the cold plasma controller 32, and hot plasma generator 33,can be assembled outside the SSHE structure into a container whoseoverall geometry and dimensions are the same of those of a conventionalhigh capacity ion-lithium battery, nominally 6×4×2 inches.

In FIG. 5, a preferential but not limiting SSHE configuration is shown.The dimensions of the SSHE are directly proportional to the desiredpower output starting from a minimum of 20 W electric with dimensionssmaller than a soda-can, up to kilowatt power ranges with proportionallyincreased dimensions. In FIG. 5, the water sealing system is formed by arapid spring-loaded double gate valve 27 b operated by the user orautomatically by the CPU structure in case of detection of water in thesurrounding on the SSHE unit.

In FIG. 6, as a complete turn-key system the SSHE work unit 22 b ismounted inside a container 39 supporting an external fuel tank 40, theswitching power supply 41 (with internal capability for multiple voltageoutputs: 12, 5, 3.3 Volts), and a rechargeable battery 42 for start-upand silent mode operations. A JP-8 fueled SSHE assembled in theconfiguration shown in FIG. 6 can be made with dimensions similar tothose currently shown by a disposable or rechargeable battery, nominally6×4×2 inches. The surfaces of container 39 exposed to the environmentallow extensions for condensing cavities 43 to further reduce thermalsignature of the unit. The supporting container 39 is equipped withstrap-on connectors for easy wear-ability and integration on the useruniform/equipment. The sides of the container exposed to the environmentcan also provide protection from puncturing the SSHE parts since theycan be made with bullet-proof materials, further reducing acousticsignature. Container 39 is also equipped with a display 45 a driven bythe CPU structure 25 a indicating fuel consumption and availability, astart-up 46 a and silent mode or shut-down button 44 a, and variousconnectors for different voltage output 41 a. In this configuration theSSHE unit is simplified by the elimination of its internal fuel tank 30a (FIG. 2), cold and hot plasma controllers 33 and 32′, and start-upand/or back-up battery 28. The CPU system integrated inside the SSHEunit is connected to the power pack 39 by means of an electricalconnector 47 also equipped with hydraulic connections to receive fuelfrom external tank 40. In FIG. 7 the SSHE unit shows the mechanicalcoupler 44 available for mechanical connection to all utilitiesrequiring mechanical shaft power rather than electric power. However,the CPU structure integrated the SSHE unit can be programmed to providea desired torque at the mechanical coupler 44 while providing electricpower at its electric output. This concludes the technical descriptionof the Small Scale Hybrid Engine operating with fossil fuels.

1. A small-scale hybrid engine comprising: a combustion chamberconfigured to generate heat energy from combustion of a combustiblefuel; a turbine coupled to a shaft and configured to convert the heatenergy into a mechanical energy to rotate the shaft; a fluid channelhaving a surface in thermal contact with the combustion chamber, whereina portion of the heat energy in the combustion chamber is transferred toa fluid flowing through the fluid channel; and a second turbine coupledto the shaft and configured to convert the heat energy transferred tothe fluid to rotate the shaft, wherein the surface defines at least aportion of the inner surface of the combustion chamber, and wherein thefluid flowing through the fluid channel does not mix with thecombustible fuel or combustion product of the combustible fuel.
 2. Asmall-scale hybrid engine as defined in claim 1, further comprising agenerator for generating electricity from rotation of the shaft.
 3. Asmall-scale hybrid engine as defined in claim 1, further comprising astarter for rotating the shaft by an external source of power.
 4. Asmall-scale hybrid engine as defined in claim 3, wherein the externalsource of power includes a battery.
 5. A small-scale hybrid engine asdefined in claim 1, wherein the fluid channel is separated from thecombustion chamber, so that the fluid does not mix with the combustiblefuel.
 6. A small-scale hybrid engine as defined in claim 1, furthercomprising a generator-starter mechanism configured to generateelectricity from rotation of the shaft and to rotate the shaft by usingan external source of power.
 7. A small-scale hybrid engine as definedin claim 6, wherein the generator-starter mechanism includes a rotatingdisk controlled by a controller.
 8. A small-scale hybrid engine asdefined in claim 7, wherein the controller includes a computer processorand a sensor adjacent to the rotating disk.
 9. A small-scale hybridengine as defined in claim 7, wherein the rotating disk includes atleast one magnets magnetically coupled a stationary coil, the stationarycoil controlled by the controller, so that the rotating disk iscontrolled by the controller.
 10. A small-scale hybrid engine as definedin claim 1, wherein the second turbine includes at least one vaporturbine coaxially positioned along the shaft and connected to a firstset of gear system.
 11. A small-scale hybrid engine as defined in claim10, further comprising a second set of gear system for indirect couplingof the vapor turbine with the shaft.
 12. A small-scale hybrid engine asdefined in claim 10, further comprising a second set of gear system forproviding an external mechanical coupling.
 13. A small-scale hybridengine as defined in claim 1, further comprising at least one airbleeding system to allow cooling of burned combustible fuel.
 14. Asmall-scale hybrid engine as defined in claim 1, further comprising anigniting system to ignite the combustible fuel.
 15. A small-scale hybridengine as defined in claim 14, wherein the igniting system includes afuel pump configured to pressurize the combustible fuel.
 16. Asmall-scale hybrid engine as defined in claim 1, wherein at least aportion of the engine is lined with acoustically absorbing materials.17. A small-scale hybrid engine as defined in claim 1, wherein thesecond turbine is directly coupled to the shaft.
 18. A small-scalehybrid engine as defined in claim 1, wherein the second turbine isindirectly coupled to the shaft through a set of gear system, the gearsystem, permitting the second turbine to rotate at a speed differentfrom that of the turbine.
 19. A small-scale hybrid engine as defined inclaim 1, further comprising at least one of an integrated fuel tank, astart-up battery, and a back-up battery.
 20. A small-scale hybrid engineas defined in claim 1, further comprising a display unit for displayingstatus of the engine.
 21. A small-scale hybrid engine comprising: acombustion chamber configured to generate heat energy from combustion ofa combustible fuel; a turbine coupled to a shaft and configured toconvert the heat energy into a mechanical energy to rotate the shaft; afluid channel having a surface in thermal contact with the combustionchamber, wherein a portion of the heat energy in the combustion chamberis transferred to a fluid flowing through the fluid channel; a secondturbine coupled to the shaft and configured to convert the heat energytransferred to the fluid to rotate the shaft; and a cooling channel forcondensing the fluid, wherein the surface defines at least a portion ofthe inner surface of the combustion chamber.
 22. A small-scale hybridengine as defined in claim 21, wherein the cooling channel is separatedfrom the fluid channel by an insulator.
 23. A small-scale hybrid enginecomprising: a combustion chamber configured to generate heat energy fromcombustion of a combustible fuel; a turbine coupled to a shaft andconfigured to convert the heat energy into a mechanical energy to rotatethe shaft; a fluid channel having a surface in thermal contact with thecombustion chamber, wherein a portion of the heat energy in thecombustion chamber is transferred to a fluid flowing through the fluidchannel; a second turbine coupled to the shaft and configured to convertthe heat energy transferred to the fluid to rotate the shaft; and an airmanifold having an inlet and an outlet, the manifold having a surface inthermal contact with the fluid channel, wherein the fluid flowingthrough the fluid channel does not mix with the combustible fuel orcombustion product of the combustible fuel.
 24. A small-scale hybridengine as defined in claim 23, further comprising an air compressorconfigured to compress the air flowing into the air manifold.
 25. Asmall-scale hybrid engine as defined in claim 24, further comprising athermal insulator separating the air compressor from the combustionchamber.
 26. A small-scale hybrid engine as defined in claim 24, whereinthe compressor is a compressor turbine powered by the shaft.
 27. Asmall-scale hybrid engine comprising: a combustion chamber configured togenerate heat energy from combustion of a combustible fuel; a turbinecoupled to a shaft and configured to convert the heat energy into amechanical energy to rotate the shaft; a fluid channel having a surfacein thermal contact with the combustion chamber, wherein a portion of theheat energy in the combustion chamber is transferred to a fluid flowingthrough the fluid channel; and a second turbine coupled to the shaft andconfigured to convert the heat energy transferred to the fluid to rotatethe shaft, wherein the fluid channel includes a cavity formed betweenthe combustion chamber and an insulator, wherein the fluid flows throughthe cavity and expands.
 28. A small-scale hybrid engine as defined inclaim 27, wherein: the combustion chamber is an elongated cylinder; theinsulator is a concentric cylinder surrounding the elongated cylinder;and the cavity is a gap between the elongated cylinder and theconcentric cylinder.
 29. A small-scale hybrid engine comprising: acombustion chamber configured to generate heat energy from combustion ofa combustible fuel; a turbine coupled to a shaft and configured toconvert the heat energy into a mechanical energy to rotate the shaft; afluid channel having a surface in thermal contact with the combustionchamber, wherein a portion of the heat energy in the combustion chamberis transferred to a fluid flowing through the fluid channel; a secondturbine coupled to the shaft and configured to convert the heat energytransferred to the fluid to rotate the shaft; and a fluid injector forthrottling the fluid into the fluid channel, wherein the fluid flowingthrough the fluid channel does not mix with the combustible fuel orcombustion product of the combustible fuel.
 30. A small-scale hybridengine as defined in claim 29, wherein the fluid injector includes acheck valve.
 31. A small-scale hybrid engine comprising: a combustionchamber configured to generate heat energy from combustion of acombustible fuel; a turbine coupled to a shaft and configured to convertthe heat energy into a mechanical energy to rotate the shaft; a fluidchannel having a surface in thermal contact with the combustion chamber,wherein a portion of the heat energy in the combustion chamber istransferred to a fluid flowing through the fluid channel; a secondturbine coupled to the shaft and configured to convert the heat energytransferred to the fluid to rotate the shaft; and an igniting system toignite the combustible fuel, wherein the igniting system includes a setof plasma electrodes, and wherein the fluid flowing through the fluidchannel does not mix with the combustible fuel or combustion product ofthe combustible fuel.
 32. A small-scale hybrid engine as defined inclaim 31, wherein the set of plasma electrodes comprises at least onehot plasma electrode and at least one cold plasma electrode, wherein thehot plasma electrode and cold plasma electrode are controlled by aplasma controller and generator.
 33. A small-scale hybrid enginecomprising: a combustion chamber configured to generate heat energy fromcombustion of a combustible fuel; an igniting system to ignite thecombustible fuel, a turbine coupled to a shaft and configured to convertthe heat energy into a mechanical energy to rotate the shaft; a fluidchannel having a surface in thermal contact with the combustion chamber,wherein a portion of the heat energy in the combustion chamber istransferred to a fluid flowing through the fluid channel; and a secondturbine coupled to the shaft and configured to convert the heat energytransferred to the fluid to rotate the shaft, wherein the surfacedefines at least a portion of the inner surface of the combustionchamber, wherein the igniting system includes a fuel expanding cavityconfigured to produce a jet of superheated fuel.